This book has many Olympiad math questions with solutions. Also in appendix it provides a summary of many math theories, formulas which is handy.
This book is brilliant. It has tons of outside-the-box, deep thinking problems to complement the more ordinary 4th-7th grade curriculum of fractions, decimals, and intro algebra/geometry. The problems are so creative, so interesting. The problems were so engaging that the kids mostly taught themselves, with some hints and tricks from me.
If you have a child who thinks that math is easy and not challenging, this book is a "must have". The problems are fun and non-standard. They require thinking and understanding of the material. All the problems and ways to solve them are explained in the book.